Brake control means



June I), 1941. s AIKMAN BRAKE CONTROL MEANS Filed Jan. 12, .1940 4Sheets-Sheet 1 INVENTOR BURTON SAIKMAN I AT'II'ORNEY F Qb June 10, 1941.

s. AIKMAN BRAKE CONTROL MEANS- 4 sheetssheet 3 Filed Jan. 12, 1940INVENTOR BURTON SAIKMAN J lllllllrllv mz mm m AQ v9 ATTORNEY June 1941-B. s. AIKMAN BRAKE CONTROL MEANS 4 Sheets-Sheet 4 ,Filed Jan. 12, 1940NNM WNW ohm x Vnn C,

INVENTOR BURTON SAIKMAN ATTORNEY Patented June 10, 194i 1 i STATES PAT rBRAKE CONTROL MEANS Burton S. Aikman, Wilkinsburg, Pa., assignor to TheWestinghouse Air Brake Company, Wilmerding, Pa., a corporation ofPennsylvania Application January 12, 1940, Serial No. 313,513

9 Claims. (Cl. 303-21) sliding of vehicle Wheels during application of ithe brakes.

It is well known that sliding of vehicle Wheels due to application ofthe brakes thereon is objectionable, both because of damage done to thewheels and because of the reduced retarding effect which is produced bya sliding wheel. As a consequence, it is desirable that means beprovided which Will detect an incipient stage of wheel sliding and thenoperate immediately to correct the condition and permit the wheel toassume normal rotation. The. incipient stage of wheel sliding isgenerally referred to as a slipping condition of the wheel, that is tosay, a wheel is said to slip when it rotates at a speed below that ofnon-slipping wheels, and is said to slidewhen not rotating at all andheld in a locked state.

An object of my invention is to provide an improved fluid pressurecontrolled apparatus which is responsive to a slipping condition of avehicle wheel and thereby rendered automatically operative to governoperation of the brakes on the slipping wheel so as to correct the causeof the slipping condition.

Another object of the invention is to provide fluid pressure controlledmeans having'a mechanism operatively responsive to an abnormal or suddenreduction in the rotative speed of a vehicle wheel, resulting in initialslipping thereof during application of the brakes, to effect quickrelease of the braking force, thereby preventing sliding of the wheels.

Other objects and advantages of the invention will appear in thefollowing more detailed description thereof, taken in conjunction withthe accompanying drawings, in which Fig. l is a diagrammatic elevationalview,

Apparatus shown in Fig. 1

According to the invention as embodied in the equipment shown in Fig. 1of the drawings, there is provided a brake cylinder device HI which issuitably connected through the medium of rigging means, not shown, tothe usual brake mech anism associated with a wheel and axle assembly .Hof a railway truck. The truck is illustrated ing 22 within which isslidably mounted a piston 24 dividing the casing into chambers 23 and21.

The piston is operatively connected by means of a piston rod 25 to theusual brake rigging, not shown. The piston rod is contained within asleeve element 25a, which is slidably fitted in an aperture in the end2i of the casing, and has formed therein a relief port 29. A releasespring 26 is mounted within the chamber 21 for moving the piston 24toward release position when fluid under pressure is released from thechamber 23, or when fluid under pressure is supplied to the chamber 21,as hereinafter explained. The piston chamber 23 is adapted to besupplied with fluid under pressure through the medium of a pipe 23,which is connected with the supply port of the self-lapping brake valvedevice [4 and may extend throughout the train.

The brake release valve device It is adapted to respond to operation ofthe deceleration control valve device 20, as hereinafter explained, tocontrol the supply of fluid under pressure to the chamber 21 of thebrake cylinder device 10 for the purpose of preventing sliding of theWheels. This valve device comprises a casing having a valve chamber 30communicating with a fluid pressure supply pipe 3|, within which chamberis mounted a valve 32 that is carried by a piston 33 and is adapted toengage a valve seat rib 34 formed in the casing. The valve 32 controlscommunication from the valve chamber 30 to a bore 35, which communicatesby way of a pipe 36 with the chamber 2'! of the brake cylinder device[0. The piston 33 is subject to the opposing pressures of fluid in thevalve chamber 30 and in a chamber 38, which communicates with a conduit39 leading to a communication in the deceleration control valve devicehereinafter described. A restricted passage 45 formed in the piston 33provides communication between the chambers 38 and 30.

The valve 32 has a stem ll which extends through the bore and into aspring chamber 62 communicating through a port 43 with the atmosphere,which stem is normally urged downwardly to hold the valve 32 in seatedposition under the pressure of a spring "A that is interposed between acollar 45 carried by the stem and a valve element 36 slidably mountedthereon. The valve element it is in turn urged into seated engagementwith a seat rib M formed on the casing, under the force exerted by thespring 44, for closing communication between the bore 35 and theatmospheric chamber 42.

The sanding devices l1 and I8 are similarly constructed, and are securedby bolts or other suitable means on downwardly extending strut membersand 5|, which form portions of the vehicle frame I2 and are disposed onopposite sides of the usual journal box I3 associated with the wheel andaxle assembly II. The sanding device I8 is illustrated partly insection, and comprises a sand hopper having formed on the lower sidethereof a portion 56, in which is formed a sand chamber 57 thatcommunicates with a sand discharge pipe 58 adapted to direct flow ofsand to the rail adjacent the Wheel. Sand contained in the hopper 55 isadapted to flow under the force of gravity into the sand chamber 57,where it is normally retained by a bafile wall 60 formed on the casingwithin the chamber. A nozzle 6| communicating with a conduit 62 andmounted in the casing portion 55 within the sand chamber 51 is adaptedto direct flow of fluid under pressure through the chamber for drivingsand over the baffle wall 6%] and through the sand pipe 58. The conduit62 is adapted to be supplied with fluid under pressure in response tooperation of the deceleration control valve device 20 as hereinafterexplained.

It will be understood that the sanding device I I has the sameconstruction as that of the sanding device I8. The sanding mechanism I Iis adapted to be supplied with fluid under pressure by way of a conduit64 for depositing sand on the rail through the medium of a sanding pipe65.

The acceleration control valve device 25 comprises a casing structureincluding a main section In secured by suitable means, such as bolts II,to the journal box I3, a reservoir portion 74, a pump portion 15, and avalve portion I6. Formed within the reservoir portion Id of the casingstructure is a liquid supply chamber I8 which is adapted to be filledwith a suitable liquid, such as oil. The pump portion I5 of the casingstructure is disposed partly within the chamber 18 and has formedtherein a pair of connected circular chambers 19 within which arerotatably mounted two intermeshed pumping gears and 8!. The gear BI ismounted on a pin or shaft 83 which is suitably journaled in the casingstructure, and the other gear 86 may be secured to an extension Ila ofthe vehicle axle by means of a key M. The pumping gears 85 and BI areadapted to be operated to supply liquid from the supply chamber I8 toeither of two oppositely disposed receiving passageways 85 and 81,depending upon the direction of rotation of the wheel and axle assemblyII, as hereinafter explained.

The passageway 86 communicates with an inlet valve chamber 88 whichcontains an inlet valve 89 for controlling communication to the valvechamber from a vertically disposed intake conduit 90 that extends to thelowermost portion of the supply chamber 18. Similarly, the passageway 81communicates with an inlet valve chamber 92 containing an inlet valve 93which controls communication between the valve chamber and an intakepipe 94 opening into the sup- 7 ply reservoir I8. Both of thepassageways 86 and 81 also communicate with discharge valve chambers 96and 91, respectively, which are connected together by way of a passage98. Discharge valves 99 and I08 are disposed in the valve chambers 96and 91 for preventing back flow of liquid to the respective passageways86 and 81.

Formed in the valve section IE5 of the casing structure and preferablyextending longitudinally thereof is a bore I02, which communicatesdirect- 1y with the discharge valve chamber 91 and by way of passage 98with the discharge valve chamber 96. Slidably mounted in the bore IE2 isa piston 563 having formed at one side thereof a chamber I04. The pistonIE3 is. adapted to vary the flow area of a port H36 connecting the boreI92 with a passageway I01, which communicates by way of a dischargechamber I98 and pipe IE9 with the liquid supply reservoir 13. The portIllG has a restricted portion I050], through which liquid can flow at arestricted rate from the bore I 02 to the passageway IG'I when thepiston N13 is disposed in the normal position thereof, as shown in Fig.1 of the drawings. The passageway I61 also communicates with the chamberI04 through a restricted port H8, and also by way of a valve chamber IIIcontaining a release ball check valve H2. The ball check valve H2 isurged toward seated position under the force of a spring H3, so thatliquid can flow from the passageway I61 to the chamber I94 only by wayof the restricted port I Iii, while flow of liquid in the oppositedirection may be affected both by way of the port H0 and past the checkvalve.

The piston I03 has a longitudinal bore H5 in which is slidably mounted asmaller piston I It having secured thereto a hollow stem II? that isslidably mounted in a bore formed in an extension IIB of the largerpiston I93, which extension is in turn slidably mounted in a boreextending between the bore H12- and chamber H38. The hollow stem I I Iis provided'with openings I21 connecting the bore 5- through theinterior passage-I22 of the stem with openings I23, which communicatewith the chamber Hill at all times. At the side of the piston I I6opposite the bore II5 is formed a valve chamber I25, within which ismounted a release valve 526 that is. adapted to control cormmmication between the valve chamber. I25 and the chamber we. The release valve I26is provided with a restricted port 28 for permitting restrictedcommunication between the chambers I25 and IE4 at all times, and isnormally urged into seated engagement with an annular seat member I29which is interposed between the end of the piston Hi3 and a coil springISllmounted within the chamber I04. The release valve IE6 is thus urgedtoward seated position under the force of a small coil spring I3I whichis interposed between .a collar on the end of a stem I32 of the valve,and an aperturedseat member I33 engaging the seat member I29. I

To the end of the hollow stem II'I within the chamber I68 is secured avalve stem I36, which is slidably mounted in a bore I31 formedin thecasing and has a fluted portion I38 carrying a valve I39. The valve I39is disposed in a valve chamber I46 and is urged toward seated positionunder the force of a spring I 42 for normally closing communicationbetween the valve chamber and a passage I43 communicating with avalvechamber I44. The valve chamber I46 is connected by way of a passage I45with the conduit 39 leading to the piston chamber 38 of the brakerelease valve device I6.

The valve I39 is adapted to control the supply of fluid under pressureto either of the sanding devices I1 and I8 in accordance with operationof a sanding selector mechanism, which includes a valve element I48disposed within the valve chamber I44 and connected by means of a stemI49 with a valve I56 that is disposed within a valve chamber I5Iformedin the casing. The valve I48 is adapted to control communicationfrom the chamber I44 by way of the bore containing the stem I49 to thesanding conduit 62, and carries a cage portion I53 having slidablymounted therein a plunger terminating in a valve I54, which is adaptedto control communication from the chamber I44 through a passage I55 tothe other sanding conduit 64. A coil spring I5! is interposed betweenthe upper surface of the valve I48 and the lower surface of the plungercarrying the valve I54 for urging said elements apart, the spring beingof such length as to hold the valve I54 in seated position only when thevalve I48 is lifted from its seat as hereinafter explained. The chamberI5I is open to the atmosphere by way of an opening I66 and has slidablymounted therein a piston I6I, which is adapted to operate the valves I56and I48 and has formed at the lower side thereof a chamber I62communicating by way of a pas- 1 sage I63 with the chamber 92. A coilspring I64 is interposed between a wall of the chamber I5I and thepiston I62 for normally positioning the piston as shown in NH, and forthereby maintaining the valve I48 in seated position.

' Operation When the fluid pressure brake equipment shown in Fig. 1 isin condition for operation, fluid under pressure supplied to thereservoir I5 in the usual manner flows therefrom through the supply pipe3I to the chamber 36 of the brake release valve device I9, and thenceflows by way of the restricted port 46 in piston 33 to the pistonchamber 38, and through the conduit 39 and passage I45 to the valvechamber I46 in the deceleration control valve device 26. It will beunderstood that the coil spring I22 normally maintains the valve I39 inseated position as shown in the drawings. With the brake valve device I4in release position, the piston chamber 23 in the brake cylinder deviceIII is maintained in communication with the atmosphere by way of thepipe 28 and the usual communications in the brake valve device.

Assuming that the. vehicle is operated along the track in a direction tocause rotation of the wheel and axle assembly II in a counterclockwisedirection, it will be apparent that the pumping gears 86 and BI aredriven at a speed corresponding to the rotative speed of the wheel todraw liquid from the supply chamber 73 through the intake pipe 94, pastthe check valve 93, and thence through the chamber 92 and passage 87 tothe gear chambers I9, from which liquid is forced through the passage66, past the discharge check valve 66, and through the chamber 96,passage 98 and chamber 91 to the bore I62. The pressure of liquid thussupplied to the bore I62 acts against the piston I63 to move the pistonagainst the opposing force of the spring I36 and thus causes the pistonto partially uncover the port I66, through which liquid under pressurethen flows to the passageway I61. Liquid in the passageway I61 is freeto flow therefrom to the chamber I68 and pipe I69 and thus to return tothe supply chamber 78.

Liquid thus supplied to the passageway I 61 also flows through therestricted passage III] to the chamber I64, and thence by way of therestricted port I26 in the valve I26 to the chamber I25. I have foundthat the liquid will displace any air initially filling these chambersafter a short period of operation.

It will be understood that the extent of movement of the piston I63 touncover the port I66 is determined by the pressure of liquid supplied tothe bore I62 by operation of the pumping gears 36 and 8I, which are inturn driven in accordance with the speed of rotation of the associatedwheel II of the vehicle. As the speed of the vehicle increases, thepiston I 63 will consequently be moved farther toward the lefthand inorder to permit increased flow through the port I66 of liquid underpressure supplied by the pumping gears 89 and SI. As the piston I 63thus moves against the force of the spring I66, the spring seat memberI29 and valve I 26 are carried with the piston while liquid is at thesame time forced from the chamber I64 through the restricted port I28 ofthe valve into the chamber I25. The smaller piston H6 of course remainsstationary at this time due to engagement of the valve I39, carried onthe end of the piston stem, with its seat.

The pressure of liquid within the chambers I25 and I64 is substantiallythe same as the fluid pressure within passage I61, chamber I66 and thesupply chamber I8, which at this time may be approximately atmosphericpressure. The pressure of liquid within the intake pipe 94 and valvechamber 92 through which liquid is drawn by operation of the pumpinggear is somewhat less than the fluid pressure in the supply chamber I6,so that the piston IBI, which is subject to the pressure of liquidsupplied to chamber I62 from valve chamber 92, is held in the normalposition as shown in Fig. 1, under the force of spring I64. The sandingvalves I48 and I49 are thus maintained in their respective seated andunseated positions, while the valve 554 is held in unseated position.

When it is desired to effect an application of the brakes, theself-lapping brake valve device I4 is operated to effect supply of fluidunder pressure from the reservoir I5 to the supply pipe 28 and thence tothe piston chamber 23 of the brake cylinder device III. The piston 24 isthereby moved against the force of the spring 26 and through the mediumof the piston rod 25 and associated brake rigging members, not shown,effects application of the usual brake shoes or other braking means tothe wheel and axle assembly II. The portion of the sleeve member 25ahaving the port 29 is thus carried outwardly of the cylinder end 2i.

If the consequent deceleration of the'vehicle is effected at a ratecorresponding to the rate of deceleration of the wheel I I, so that anytendency of the wheel to slip on the rail is avoided,

the pressure of liquid supplied to the bore H32 by the pumping gears 89and 3! is reduced gradually, so that the spring i333 is perrn ted toshift the spring seat member I29, valve IZii, and piston N33 to theright slowly enough to force liquid from the chamber I through therestricted port I28 to chamber I84 without exerting sumcient pressure onthe piston 1 it to overcome the force of spring N52. The valve itil isthus stili maintained in seated posi ion.

If, however, the application of the brakes causes retardation of thewheel H at an excessive rate, so that the wheel begins to slip withrespect to the rail, the relatively rapid reduction in speed ofoperation of the pumping gears 81? and 8| effects a correspondinglyquick reduction in the pressure of liquid in the bore Hi2 acting on thepiston ltd. The spring 539 is thereby enabled to shift the spring seatmember E29, valve 526 and piston illS toward the normal position at aspeed somewhat in excess of that which would permit completedisplacement of liquid from the chamber i253 by way of the restrictedport I23, so that liquid is momentarily entrapped within the chamber I25and thus transmits sufficient pressure exerted by the spring i323through the medium of the stem it? and valve E38 to overcome the forceof spring M2.

The valve I39 is thereby moved slightly away from its seat forpermitting relatively restricted I now of fluid under pressuretherepast, it being understood that the valve is not, under theoperating condition now being described, moved to its fully unseatedposition. Fluid under pressure is supplied at a relatively slow rate offlow from the supply pipe through the chamber 39 in the brake releasevalve device It, the restricted port in the piston 33, chamber 38,conduit 39, passage I in the deceleration control valve device 26, andthen past the slightly unseated valve I39 and through passage I43,chamber I44, passage I and conduit 64 to the sanding device H, which isthereby operated to supply sand through the sanding pipe to the rail inadvance of the wheel II. The presence of sand on the rail will usuallyincrease the coefiicient of friction between the rail and wheel IIsufficiently to cause the wheel to pick up or increase its rotativespeed in time to avoid serious wheel slipping. Upon the resultantincrease in the speed of operation of the pumping gears 83 and BI,further reduction in pressure of liquid in the bore I02 is prevented.Meanwhile, due to continued flow of liquid from the chamber I25 throughthe restricted port I28 of valve I26, the

spring I42 becomes effective to permit the piston H6 to be returned toits normal position under the force of the spring I42, while the valveI39 is again moved to seated position. Further supply of sand to therails is thus stopped.

Let it now be assumed that an application of the brakes is efiected withsuch force as to cause deceleration of the wheel and axle assembly II ata rate in excess of the maximum rate permissible without causing wheelsliding, with the result that the speed of operation of the pumpinggears 8d and BI is rapidly reduced, thus causing a relatively suddendecline in the pressure of liquid supplied to the bore I92. Upon thequick reduction of liquid pressure within the bore I62 the piston Hi3and spring seat member I29 are rapidly shifted under the force of thespring I3ll toward normal position. As the spring seat member I29 andthe valve I26 seated thereon are thus quickly moved toward the pistonH5,

liquid is entrapped therebetween due to the slow rate of flow permittedby the restricted port I28, and the piston H6, stem Ill, and valve I39are consequently forced to the right under the pressure of the springI30 in opposition to the pressure of the spring I42. Because of thesudden movement of the piston I93, spring seat member I29 and valve I26under the force of the spring I30 as just explained, only a relativelysmall amount of the liquid entrapped within the chamber I25 has time toflow therefrom to the chamber I84 by way of the restricted port I28, sothat substantially the full force of the spring I38 is transmitted tothe piston Ht, which is thus operated to move the valve I33 to its fullyunseated position.

With the valve 139 thus unseated, fluid under pressure is vented fromthe piston chamber 38 of brake release Valve device IE3 by way of theconduit 33, past the unseated valves I39and I54 and through conduit I64to the sanding device I! at a faster rate than that of flow of fluidfrom the chamber 30 through the restricted port 48 in piston 33.Consequently, while the sanding device I! is thereby operated in theusual manner to elTect supply of sand through the sanding pipe 65 to therail in advance of the wheel, the pressure of fiuid in the chamber 38moves the piston 33 upwardly and thereby lifts the valve 32 away fromthe seat rib 34, the valve 65 being meanwhile maintained in engagementwith the seat rib 47 under the force of the spring 44, which force isnow greater than is normally the case, due to compression of the spring.

When the valve 32 is thus unseated, fluid under pressure is suppliedfrom the supply pipe 3I by way of the chamber 36 and pipe 3t to thechamber 2'? in the brake cylinder device I9, the piston 24 of which isthen quickly moved toward release position by the force of the spring 26upon substantial equalization of the pressures in chambers 23 and 21.

In response to the release of the brakes initiated as just explained,the wheel and axle assemly II, aided by the increased traction resultingfrom the depositing of sand on the rail, again picks up-speed until therotative speed thereof corresponds with that of the vehicle, while thepumping gears 89 and El are driven to increase the supply of liquidunder pressure to the bore I02 for again shifting the piston I 63 andassociated elements to the left against the force of the spring I30.Upon the quick movement of the piston I93 as just explained, the liquidwithin the chamber I 84 is for a time subjected to a slightly increasedpressure, since flow of liquid from the chamber through the restrictedpassage Ii0 to the passageway I0! is restricted while the spring II3resists opening of the check valve II2, and the valve I26 isconsequently unseated against the biasing force of the spring I 3! foradmitting liquid under pressure from the chamber I04 to the chamber I25,where the pressure of the liquid is eil'ective through the medium of thepiston II B and stem 4 ll to maintain the valve I33 unseated,

It will thus be seen that, during such time as is required for the speedof rotation of the axle assembly II to increase from the rate at whichit began to slip to a rate corresponding to the vehicle speed, fluidunder pressure is continuously supplied from the piston chamber 38 ofbrake release valve device It to the sanding device i1, while the valve32 is maintained unseated for supplying fluid under pressure to thechamber 21 of the brake cylinder device I0, as hereinbefore explained.In other words, the rail is sanded and the brakes held released topermit complete restoration of the rotative speed of the wheel and axleassembly to a rate corresponding with the speed of the vehicle.

The return of the rotative speed of the Wheel II to a valuecorresponding to the speed of the vehicle, following the temporaryrelease of the brakes as explained, is usually effected rapidly, andwhile the brakes associated with other wheels of a vehicle are stillmaintained applied. It is consequently desirable that a reapplication ofthe brakes for the wheel II be eifected automatically after the wheelslipping condition has been corrected.

After movement of the piston I03 under the increased pressure of liquidin the bore I02 has been completed during restoration of the rotativespeed of the wheel to the vehicle speed, the pressure of liquid in theconnected chambers I34 and I25 again becomes equalized with that of thepassageway I91. The valve I39, which had been maintained unseated by thepressure of liquid in the chamber I25 during the aforementionedoperation of the acceleration control valve device 29, is then moved tothe left to seated position under the force of the spring I42, the stemH1 and piston H6 being moved in the same direction to expel liquid fromthe chamber through the restricted port I28 in valve I 25, which ismeanwhile returned to seated position by the spring I3I. When the valveI39 is thus moved to seated position, further flow of fluid underpressure to the passage I43 and thence to the sanding device I1, isstopped, while the pressure of fluid in the chamber 38 of the brakerelease valve device I9 is quickly increased toward equalization withthe fluid pressure in chamber 30, by flow of fluid through therestricted port 4|]. When the fluid pressures in chambers 39 and 33become equalized, the piston 33 is operated to move valve 32 intoengagement with the seat rib 34, under the force exerted by the spring44 on the stem 4I, so that the supply of fluid g':

under pressure to the chamber 21 of the brake cylinder device I9 is outoff, while fluid under pressure begins to flow from the chamber 21 toatmosphere by way of pipe 36, bore 35, and past the valve member 46. Thespring 44 at this time exerts only its normal force to oppose unseatingof the valve, since the collar 45 has been returned to the lowerposition as shown in Fig. 4.

Assuming that the supply of fluid under pressure by way of the brakevalve device I4 and the pipe 28 to the piston chamber 23 of the brakevalve device is still continued, the piston 24 is again forced to theright against the pressure of the spring 26 for effecting reapplicationof the brakes. The spring 44, however, is adapted to move the valveelement, 46 into engagement with the seat 41 for cutting oiT completeflow of fluid under pressure from the spring chamber 21 when the fluidpressure therein has been reduced to a predetermined value, it beingunderstood that the port 29 of the sleeve 25a is still held outwardly ofthe end 2| of the brake cylinder casing, so that the fluid pressureacting in the chamber 23 on the brake cylinder piston 24 is noteffective to cause reapplication f the brakes to the same degree offorce as existed prior to the slipping of the wheel.

When it is desired to effect the release of all brakes on the vehicle,the valve device I4 is moved to release position for venting the pipe 28and brake cylinder chamber 23 to the atmosphere, whereupon the spring 22moves the piston 24 and rod to release position. As the port 29 in thehollow brake cylinder rod 25 is thus brought into communication with thechamber 21, the fluid under pressure remaining therein is discharged tothe atmosphere, so that the brake cylinder device is then in conditionfor subsequent operation to effect application of the brakes in theusual manner.

If the vehicle is driven along the rail in the opposite direction, sothat the wheel and axle assembly I I is rotated in a clockwisedirection,

' the pumping gear 80 is likewise rotated in a clockwise direction forturning the pumping gear 8i in a counterclockwise direction, therebydrawing liquid from the supply reservoir 18 through the intake pipe 93,past inlet valve 89, and through chamber 88 to the chamber 19, fromwhich the liquid is forced under pressure through the passage 81 andpast the discharge valve I00 to the bore I02 for operating the pistonI03 in the manner hereinbefore explained. At the same time liquid underpressure is supplied from the passage 81 through chamber 92 and passageI63 to the piston chamber I62, and moves the piston I6I upwardly againstthe force of the spring I64, thereby seating the valve I and unseatingthe valve I48. As the valve I48 is moved upwardly and away from its seatthe valve I54 is lifted into seated position under the pressure of thespring I51. The several valve elements are thus positioned to conditionthe sanding device I8 for operation, while the sanding mechanism I1 atthe trailing side of the wheel and axle assembly I I is renderedinoperative.

If an application of the brakes is now effected with excessive force,causing the wheel II to slip with respect to the rails so as to eifectoperation of the deceleration control valve device 20 in the mannerhereinbefore explained, the consequent unseating of the valve I39 willeffect supply of fluid under pressure in the usual manner from the valvechamber I49 and through the passage I43 and chamber I44, past theunseated valve I43, and through the conduit 62 and nozzle BI to sandchamber 51 of sanding device I8. Sand is thereby driven from the sandchamber and through the sand pipe 58 to the rail in advance of the wheelI I.

Equipment shown in Fig. 3

A somewhat different form of brake control apparatus embodying featuresof the invention is shown in Fig. '3 of the drawings, which illustratesbraking equipment adapted for association with a single wheel, or wheeland axle assembly of the vehicle. A vehicle truck is shown infragmentary form in Fig. 3 and includes a wheel and axle assembly I10,which is rotatably mounted in suitable journal assemblies such as I1I,that are in turn adapted to carry a truck frame structure I12. The brakecontrol apparatus comprises a deceleration control valve deviceindicated generally by the character I13, and a brake cylinder deviceI14 having associated therewith a brake release valve device I15.

The brake cylinder device I14 comprises a cylinder casing I18 havingslidably mounted therein a piston I 19, which has formed at one'sidethereof 'a piston chamber I to which fluid under pressure may besupplied by way of suitable communications including a pipe I8I. Thepiston I19 has a piston rod I84 which is suitably connected to the usualbraking means associated with the wheel and axle assembly I16, and isdisposed within a spring chamber E85 formed at the side of the pistonI'it opposite the chamber 583. A coil spring I8! is interposed betweenthe piston Ill and the end Wall of chamber I85 for urging the pistontoward release position as shown in the drawing.

The brake release valve device I'iii comprises a casing Q89 which issecured to the casing N8 of the brake cylinder device by suitable means,not shown, and which has formed therein a bore in which is mounted apiston I98 having a valve portion lat. he valve portion RSI is adaptedto engage a seat rib I92 formed on the casing adjacent an interiorpassage 593, which communicates through a passage 2W with chamber I85and with the atmosphere by way of an open cavity i9 3. Within the cavityI9 3 is mounted a valve H5 that is connected to the valve portion iiliby means of a stem Hi6 extending through the passage I93. The valve I95is adapted to be moved into engagement with a seat rib I91, but isnormally held spaced therefrom while the valve portion ifiI engages theseat rib I92 as shown in the drawing. At one side of the piston ISI isformed a chamber 250 which communicates with a conduit 2c! leading to avalve chamber of the deceleration control valve device I13 hereinafterdescribed. The chamber 2&0 also communicates by way of a restrictedpassage 254 and a valve chamber 253 with a port 25411 in the wall of thepiston bore containing the brake cylinder piston 219, which port isadapted to communicate with chamber E89 upon initial movement of thepiston toward brake application position as hereinafter explained. Aspringpressed ball check valve 255 is mounted within the valve chamber253 for preventing back flow of fluid from the chamber 2% to the port213cc. At the side of the piston I95 adjacent the valve portion IQI isformed a chamber 2% which communicates with a port 299 in the wall ofthe brake cylinder piston bore that is adapted to be uncovered by thepiston H9 as it approaches its maximum brake application position.

The deceleration control valve device H3 comprises a casing structureincluding a mounting flange portion 2i5 which is adapted to be securedto the journal box structure ill by suitable means such as bolts 2 i aliquid supply reservoir portion 2! carried by the flange portion, a pumpportion 259, and a valve portion 229. The reservoir portion ZI8 of thecasing structure is provided with exterior cooling fins 222 and hasformed therein a liquid supply reservoir 224 adapted to contain aquantity of oil or other suitable liquid, which may be supplied theretoby way of a suitable aperture normally closed by a removable plug 225. Aplurality of air conduits 221 are preferably mounted within the chamber224 for cooling the liquid contained therein. The ends of the coolingconduits 22! are open to the atmosphere outwardly of the reservoirportion 258 of the casing structure and are adapted to be suitablysecured thereto by solder or other means preventing leakage of liquidfrom the chamber 224. l

The pump portion 218 of the casing structure has formed therein apumping gear chamber 239 within which are mounted a pair of pumpinggears 23I and 252, the gear 2-3I being keyed or otherwise secured to anextension Ilaia of the axle and thus adapted for rotation with the wheelI15. The pumping gear 232 is mounted on a shaft 233 which is suitablyjournaled in the pump portion of the casing structure. When the pumpinggear 23! is rotated'by the wheel and axle assembly in a clockwisedirection it is adapted to cooperate with the other gear 232 for drawingliquid from the reservoir 224 through an intake pipe 235 to the chamber25% from which liquid is forced under pressure into a passage 235, ashereinafter explained. In order to avoid complication of the drawingsthe pumping gears 23! and 232 have thus been illustrated as adapted foroperation in one direction only, but it will be obvious that by theprovision of suitable valvessuch as those shown in association withgears 8t and BI of Fig. l, the pumping mechanism could be renderedoperative for either direction of rotation of the associated wheel andaxle assembly.

The valve portion 22b of the casing structure has formed therein alongitudinal bore in which is slidably mounted a piston 243! having atone side thereof a chamber 2M communicating with passage 235 and on theopposite side thereof a spring chamber 242 communicating by way of apassage 253 with a passage 2&5 leading to the liquid sup-ply chamber225. A coil spring 248 is interposed between the end wall of the chamber252 and the piston 25B for urging the piston into engagement with theend of a cylinder mem her 253, which extends concentrically within thechamber 24! and has screw-threaded connection in a suitable aperture inthe end of the casing portion 22a The cylinder member 25% has a bore 25!formed therein parallel to that in which the piston 2 1i! is slidablymounted, which bore is adapted to receive an auxiliary piston 253 havinga stem 255 that is secured in a suitable manner with the piston 2 55.The face of the piston 253 adjacent the piston 2% is subject to fluidpressure in the chamber 2M, it being noted that the end of the cylindermember 255 abutting the piston 245 is provided with a plurality ofchannels 255, while the other face of the piston 253 is exposed to achamber 25! communicating with the chamber MI by way of a passage 255%formed in the stem 254. A spring pressed ball check valve 26!] isinterposed in the passage 258 for preventing flow of fluid therethroughfrom the chamber 251, although communication between the chambers 2M and25! is always maintained by way of a calibrated or restricted port 256formed in the piston 253.

The piston 249 is adapted to function in a manner similar to that ofoperation of piston I03 shown in Fig. 1, to control communication fromthe chamber 2st through port 252 having a variable flow area to thepassage 245 leading to the liquid supply chamber 224, the extent ofmovement of the piston in uncovering the port 252 being determined inaccordance with variations in the pressure of liquid supplied by thepumping gears to the chamber 2:?! as hereinafter explained. The port 262has a restricted portion 283 which is adapted to permit flow of liquidfrom the chamber 2 1! to the passage 245 at a limited rate when thepiston 2 3i} is in engagement with the end of the cylinder member 250 asshown in the drawings.

Slidably mounted in the bore 25! of the cylinder member 250, and inalignment with the piston 255, is a piston 255, which has at one sidethe chamber 251 and at the other side a chamher 256 which is open to thechamber 2M by way of apertures formed in the cylinder member. The piston255 has a stem 261 slidably mounted in a sleeve portion 268 extendinginteriorly of the cylinder member.

The stem 261 terminates in a valve 210 that is disposed in a valvechamber 21! communicating with the conduit which valve is adapted tocontrol flow of fluid under pressure from the chamber 21! to theatmosphere by way of an exhaust port 213. Surrounding the end of thestem 261 adjacent the valve 210 is an annular groove 215 whichcommunicates with a liquid return passage 214 by way of which liquidleaking past the stem 261 may flow back to the supply chamber 224. Acoil spring 211 is interposed between the end wall of the chamber 266and the piston 265 for urging the piston toward the piston 253, movementof the piston in that direction being stopped upon engagement of thevalve 10 with its seat as shown in Fig. 3.

Operation spring 2-28 by the pressure of liquid in the chamber 24!, andcarries with it the smaller piston 253, while liquid from the chamber24! fills the chamber 266, and flows by way of the restricted port 266and passage 258 to the chamber 261 between the pistons 253 and 265. Asthe piston 22!! is moved to the left, as viewed in the drawing, ituncovers the port 262 for permitting return flow of liquid underpressure from the chamber 2M through the port and passage 2 36 to thereservoir 224.

If the speed of the vehicle is reduced at a normal rate, the pumpinggears 23! and 232 are consequently operated to supply liquid to thechamber 24! at a slower rate, and as the pressure of liquid is reducedthe piston 240 and piston 263 are gradually moved to the right under thepressure of the spring 248, while liquid in the chamber 251 is permittedto flow through the restricted port 256 to the chamber 24! withoutexerting appreciable pressure on the piston 266.

When fluid under pressure is supplied in the usual manner by way of thebrake cylinder pipe I8! to the piston chamber I80 of the brake cylinderdevice I10, in initiating an application of the brakes, the piston I10and piston rod I84 are thereby operated to actuate the usual brakingmechanism associated with the wheel and axle assembly I10 in thedrawing. As the brake cylinder I10 over travels the port 204a, fluidunder pressur is supplied from the chamber I80 past the ball check valve205 to the piston chamber 200 in the brake release valve device I15, andthe piston I90 is thereby subjected to fluid pressure for insuringseating engagement of the valve I0! with the valve seat rib I92 as shownin the drawing. When the brake cylinder piston I19 moves far enoughtoward brake application position to establish communication between thechamber I00 and port 209, fluid under pressure is admitted to thechamber 208, and acts on the smaller area of the piston I90 exposed tothat chamber in opposition to the pressure of fluid in chamber 230. Itwill be noted that fluid under pressure in the chamber 200 is also freeto flow therefrom by way of the conduit 20! to the valve chamber 21! inthe deceleration control valve device I13.

If the application of the brakes effected in the manner just explainedcauses reduction in the rotative speed of the wheel and axle assemblyI10 at a rate not exceeding a predetermined safe rate of deceleration,i. e., at a rate of deceleration not likely to result in slipping of thewheels, the associated pumping gears 23! and 232 are operated at acorrespondingly decreasing rate of speed, so that the pressure of liquidsupplied to the chamber 24! is gradually reduced, while the spring 248becomes effective to shift the pistons 240 and 253 to the right andtoward the normal position illustrated in Fig. 3 of the drawings. Inthus gradually moving toward the piston 265 the piston 253 displacesliquid from the chamber 251, the liquid flowing therefrom through therestricted port 256 of the piston 253 to the chamber 2M, while thepressure of liquid acting on the piston 256 remains substantiallyconstant. The spring 211 thus still remains effected to maintain thevalve 210 in seated position as shown in the drawings.

Should the brakes be applied on the wheel and axle assembly I10 withsuch force as to cause wheel slipping, however, the speed of operationof the pumping gears 23! and 232 is consequently reduced at such a rateas to eflect a sudden reduction in the pressure of liquid supplied tothe chamber 24!, so that the spring 248 is rendered effective to movethe pistons 246 and 253 toward their normal position at a speed greaterthan that with which the liquid entrapped within chamber 251 can bedisplaced therefrom by flow through the restricted port 256. Themovement of the piston 263 is consequently transmitted through theliquid in chamber 251 to the piston 265, which, together with stem 261is moved outwardly against the force of the spring 211 to unseat thevalve 210.

With the valve 210 thus moved to unseated position, fluid under pressureis quickly vented from the chamber 200 by way of the conduit 20!,chamber 21!, past the valve, and through the atmospheric passage 213. Atthe same time, fluid under pressure is released at a slow rate from thepiston chamber I86 of the brake cylinder device by way of the passage204, past the ball check valve 205 and restricted passage 204acommunicating with the chamber 200. Upon a predetermined reduction inthe fluid pressure in chamber 200 the pressure of fluid in the chamber208 forces the piston I90 to the right as viewed in Fig. 3, therebyseating the valve I and moving the valve I0! away from the seat rib I92,for establishing communication from the chamber 206 through the passageZIii to the spring chamber I65 of the brake cylinder device. It will beunderstood that the brake application position of the brake cylinderpiston I19 is in the region of the piston bore intermediate the ports2!!! and 209, and that equalization of the fluid pressures acting onopposite sides of the piston will quickly follow the flow of fluid fromthe chamber I80 past the unseated valve I8! to the spring chamber I85.Upon substantially equalization of pressures in chambers I80 and I05 thespring I81 is rendered effective to shift the piston I19 and the usualbrake rigging elements connected thereto toward their release position.

Upon operation of the deceleration control valve device I81 to efiectthe release of the brakes as just explained, the tendency of the wheelI!!! to slide along the rail is overcome, and the wheel and axleassembly is again free to rotate at the speed at which the vehicle isthen traveling. The

associated pumping gears ii-H and 232 are con sequently operated atincreased speeds for building up the pressure of liquid in the chamber2M, the increased pressure forcing the piston 2-43 to the left againstthe pressure of the spring 248, while the piston 253 is correspondinglywithdrawn from the chamber 25?. Due to this movement of the piston 253,and also by reason of the fact that a portion of the liquid previouslyentrapped within the chamber 25? has meanwhile had time to flow throughthe restricted port 255' to the chamber 2M, the spring 2i? becomeseiiectlve to shift the piston 265, stem 25'! and valve 279 to the left,as viewed in Fig. 8, until the valve engages its seat for cutting offfurther flow of fluid under pressure from the chamber Ell to theatmosphere.

A reapplication of the brakes may then be effected, by further supplyingfluid under pressure by way of pipe lfil to the brake cylinder pistonchamber I89 for increasing the pressure in that chamber and in thepiston chamber 2% in the brake release valve device.

Upon the increase in the pressure of fluid in the piston chamber 283,the valve it! is again shifted to seated position as shown in thedrawings, while the valve B35 is unseated for venting fluid underpressure from the spring chamber H85 to the atmosphere, therebypermitting the pressure of fluid in the chamber Hill to shift thepisston N55 to brake application position.

Equipment shown Fig. 4

Still another embodiment of the invention is illustrated in Fig. 4 ofthe drawings, in which there is shown a Wheel and axle assembly 286adapted to have associated therewith the usual braking means operable bya brake cylinder device 28l, a magnet valve device 282, and adeceleration control valve device 283 which may be suitably mounted on ajournal box structure 2% associated with the wheel and axle assembly.

The brake cylinder device 28! may be of any conventional type operativeto effect application and release of the brakes, not shown, forcontrolling the wheel and axle assembly 286, and is adapted to besupplied with fluid under pressure in accordance with operation of themagnet valve device 232, which comprises a casing having a valve chamber288 communicating with a brake cylinder supply pipe 233, and havingmounted therein a pair of valves 290 and 2st. The valve 2% is adapted tocontrol communication from the chamber 258 through a bore 252 andpassage 2&3 to the atmosphere, and is normally maintained in seatedposition under the force exerted by a spring 255, which is interposedbetween one wall of a chamber 23? and a fluted stem 298 of the valve29!. The spring 235 normally maintains the valve 23! in unseatedposition as shown in the drawing, so that fluid under pressure may besupplied to the brake cylinder device 23! by way of a supply pipe 333,the chambers 2S? and 288, and supply pipe 283. Mounted in the upperportion of the casing is a magnet, indicated by the character Sill,which is adapted to be energized for effecting movement of the valves2%! and 2% to their respective seated and unseated positions, upon theclosing of an electric circuit as hereinafter explained.

The deceleration control valve device 233 comprises a casing structurehaving a pump portion 365 and a valve portion 386, which are formedintegral with or may be secured to a reservoir portion 391 which is inturn mounted on the journal box structure 266 by means of bolts sun. Thereservoir portion 38'! has formed therein a liquid supply chamber 333containing a quantity of liquid that may be supplied thereto by way of afilling opening closed by a plug 399. Formed within the pump portion.3&5 of the casing structure is a chamber 3H in which are mounted apumping gear 352 and a similar gear 3|3, the latter of which is securedto an extension 2853a of the axle, or is otherwise arranged to be drivenby the Wheel and axle assembly 23 1 The gears 3L2 and 3l3 are adapted tobe operated to draw liquid from the chamber through an intake pipe 3L5to the chamber 3i i.

The acceleration control valve device further comprises a cylindermember 3 l which is mounted within a chamber 3 59 formed in the valveportion 3%, which cylinder portion is provided with a bore havingslidably mounted therein a pair of pistons 32! and 322 that are normallyspaced apart by means of a spring 323 disposed in a chamber 323 betweenthe pistons. The piston 32! has a restricted port 32'! forming an alwaysopen communication between the chambers 3H; and 324, and is alsoprovided with a somewhat larger port 328 which is norma ly closed by avalve 33$ carried on a piston 33% subject to the opposing pressures ofliquid supplied to the chamber 3E9 and of a spring 332. The piston 33!con trols communication from the chamber 3E9 through a port 333 to adischarge passage 334 communicating with the liquid supply chamber 388.A restricted portion 333a of the port is adapted to providecommunication from the chamber 3) to the passage 334 when the piston 33|is in the normal position shown in Fig. 4.

The piston 322 has secured thereto a stem 333, which extends through achamber 339 communicating with the passage 3!?! and terminates in avalve member 349, which is normally held in engagement with a seat t llunder the force of a spring 352. interposed between the piston and thelower wall of the chamber 333. Mounted in op erative alignment with thelower surface of the valve member 34!! is a spring biased contactelement 343, which is adapted to be forced downwardly thereby intoengagement with a contact element 3M to close a circuit for energizingthe magnet 39! of the magnet valve device 232, as hereinafter explained.It will be understood that the contact elements 343 and 3% areillustrated in diagrammatic form in Fig. 4.

Operation Let it be assumed that the vehicle is moved along the track soas to cause rotation of the wheel and axle assembly 286 in acounterclockwise direction, and that the pumping gears 3|3 and 3l2 arethereby operated to supply liquid from the chamber 368 through the pipe315, chamber H and a passage 3&5 to the chamber H9 at a pressurecorresponding with the rotative speed of the wheel and axle assembly.Liquid under pressure thus supplied to the chamber 3I9 flows therefrominto the chamber 333, and through the port 328, which may be openedmomentarily due to downward movement of the piston 32l against spring323, and the restricted port 32'! in the piston 32! to the chamber 324,it being understood that air initially present in these chambers isdriven out after a short period of time. The pressure of liquid in thechamber 3H! at the same time acts against the piston 33! to force thepiston upwardly against the pressure I of the spring 332, therebyuncovering the port 333 for permitting liquid to flowfrom the chamber31.! through the passage 334 to the supply chamber 308.

As the piston 33! is moved upwardly, the spring 323 is renderedeffective to move the smaller piston 32! in the same direction, so thatthe port 328 is maintained closed by the valve 330 carried by the largerpiston. As the chamber 324 between the piston 32! and 322 is thusexpanded, liquid from the chamber 3L3 is further supplied theretothrough the restricted port 32'!. The extent of movement of the piston33!, and consequently of the piston 32!, will of course be determined bythe speed of rotation of the wheel and axle assembly 280, since thepressure of liquid supplied to the chamber 3!!! depends upon the speedat which the pumping gears 3|2 and 3I3 are operated by that assembly.

When it is desired to effect an application of the brakes, the usualbrake controlling valve device, not shown, is operated to supply fluidunder pressure through the pipe 300, chamber 29'! in magnet valve device282, chamber 298, and pipe 289 to the brake cylinder device 23!,

which is thereby operated to apply power to the usual brake riggingmechanism, not shown in the drawing. As the rotative speed of the wheeland axle assembly 289 is reduced due to application of the brakes, thepumping gears M2 and 3|3 are operated at correspondingly lower speed,while the pressure of liquid in chamber 3!9 is consequently reduced topermit gradual downward movement of the pistons 33! and 32! under theforce of the spring 332. Assuming that the application of the brakesjust described is 'efiected to a normal degree and that the wheel andaxle assembly 283 is retarded at a rate not producing sliding of thewheels, the downward movement of the piston 32! causes liquid in thechamber 324 to flow therefrom byway of the restricted port 32! to thechamber 3l9, while the piston 322 is held stationary under the forceexerted by the spring 342. The valve 34!] is accordingly maintained inengagement with the seat 34! and spaced from the contact element343.

device 282 is energized through acircuit which "includes the'positiveterminal of a battery 350,

a conductor 35!, the connected contact elements,

pressure of the spring 296 to their respective unseated and seatedpositions, thus cutting off further supply of fluid under pressure tothe brake cylinderidevice 29!, which is at the same time vented to theatmosphere by way of the unseated valve 299, bore 292, and atmosphericdischarge port 293. The'equipment is thus operative to effeet therelease of the brakes in time to prevent sliding of the wheel 280alongthe rail.

Liquid is meanwhile caused to flow from the chamber 324 between thepistons 322 and 32! through the restricted port 32'! to the chamber3l'9, due to the upward force of the spring 342 exerted through themedium of the piston 322,

which piston is finally moved upwardly'to cause reengagement of thevalve 34!! with the seat 34!,

thus permitting the contact element 343 to disengage the element 344.The circuit for energizing the magnet 33! is thereby broken, and thespring 296 of the magnet valve device then becomesefiective to move thevalve 29!] into seated position while unseating the valve 29!. With 'iluid under pressure to the brake cylinder 28! the brakes.

the valve 29! thus unseated, further supply of may beresumed forefiecting a reapplication of Summary From the iforegoing it will beapparent that a brake control equipment constructed in accordance withany of the several forms of my invention comprises liquid pumping meansoperative *in'accordance with the rotative speed of a'vehic'l'e wheel tovary the pressure of liquid acting on a movable abutment, which isresponsive to a sudden reduction in said pressure to cause quick If theapplication of the brakes is effected'with too heavy a force withrespect to the rotative speed of the wheel and axle assembly 280, sothat the wheels begin to slip and consequently to decelerate at a ratein excess of that for which the deceleration control valve device 283 isinitially conditioned, the resultant reduction in speed of operation ofpumping gears 3l2 and 3!3 effects a relatively sudden reduction in thepressure of liquid supplied to the chamber 3l9. Upon the suddenreduction of the liquid pressure in the chamber 3l9, the spring 332becomes effective to move the piston 33! and piston 32! downwardly at arapid rate, and as the liquid entrapped in the chamber 324 cannotimmediaterelease of the brakes to prevent sliding of the wheel, and isresponsive to subsequent pick-up in rotative speed of the wheel topermit reapplication of the brakes." i

While several illustrative embodiments of the invention have beendescribed in detail, it is not intendedto limit'the invention tothose'embodiments'or otherwise than by the terms of the appendedclaims."

' Having now described my invention, what I claim as new anddesire tosecure by LettersPat- 'ent, is:

' means including a pump driven by said wheel for ly be forced therefromthrough the restricted port 321, the piston 322 is consequently forceddownwardly against the pressure of the spring 342, and the valve 340 isthereby unseated. With the valve 343 unseated, liquid is uicklydischarged from the chamber 339 to the supply chamber 398 while thefluid pressure still acting on the piston 33! is reduced to that of thesup ply chamber, whereupon the spring 332 acts through the medium of theseveral pistons to shift the valve member 34!! to its lowermost positionfor moving the contact element 343 into engagement with the contactelement 344.

Upon engagement of the contact elements 343 and 3 34, the magnet 33! ofthe magnet valve supplying 'liquid' under a pressure varying inaccordance with the speed thereof, a spring, movable abutment meanssubject to the opposing pressures of said spring and 'of 'the-liquidsupplied by said pump for controlling a discharge communicationtherefor, a' piston movable relatively to the abutment means andoperative to means for gradually releasing said liquid during thebrakes, speed responsive mechanism operative to establish a fluidpressure proportional to the rotative speed of said wheel, a movableabutment subject to said fluid pressure and to a subject to said fluidpressure and to a substantially constant opposing pressure, a firstpiston having a restricted aperture and operative by said movableabutment through a chamber containing a quantity of liquid, and meansfor actuating said brake release means including a second piston subjectto the pressure of liquid in said chamher.

4. Deceleration control apparatus for governing the brakes for a vehiclewheel, comprising brake release means operable to efiect release of thebrakes, speed responsive mechanism operative to establish a fluidpressure proportional to the rotative speed of said wheel, a movableabutment subject to said fluid pressure and to a substantially constantopposing pressure, an element movable by said abutment through a chamberadapted to contain a quantity of liquid, means for effecting restrictedflow of liquid from one side of said element to the other during normalgradual movement thereof by said abutment, and means for actuating saidbrake release means including a piston subject to the pressure of liquidentrapped at one side of said element upon sudden movement thereof dueto a change in the rotative speed of said wheel at an undesirable rate.

5. Deceleration control apparatus for governing the brakes for a vehiclewheel, comprising brakes release means operable to effect release of thebrakes, a pump operative to supply fluid to a chamber at a pressureproportional to the rotative speed of the wheel, a piston subject to thevariable pressure of fluid in said chamber and to a substantiallyconstant opposing pressure, a movable abutment associated with saidpiston and having a restricted port through which fluid can flow to abore at one side thereof when operated by said piston in response to anincrease in the pressure of fluid in said chamber, a spring, and meansincluding another piston interposed between said spring and said borefor actuating said brake release means in response to pressuretransmitted through the medium of fluid entrapped in said bore due tosudden movement of said movable abutment.

6. In a brake e uipment for a wheel of a vehicle, in combination, brakerelease means operative to effect quick release of the brakes, areservoir adapted to contain a quantity of liquid, a casing having achamber, a pump operative to supply liquid from said reservoir to saidchamber at a rate proportional to the rotative speed of said wheel, aspring, a movable abutment subject to the opposing pressures of saidspring and of liquid in said chamber for varying the flow area of areturn passage leading therefrom to,

ative by the first mentioned abutment to vary the volume of a borecommunicating through a restricted port with said chamber, a pistonsubject to the pressure of liquid in said bore, and means operative bysaid piston upon a predetermined increase in pressure of liquid in saidbore for effecting operation of said brake release means.

7. Deceleration control apparatus for controlling the brakes associatedwith a wheel of a railway truck including a journal box, comprisingbrake release means operative to efiect quick release of the brakes, acasing structure adapted to be carried by the journal box associatedwith the wheel and having formed therein a liquid supply reservoir and apressure chamber, a pump mounted in said casing structure and operativeto supply liquid from said reservoir to said chamber at a rateproportional to the rotative speed of said wheel, a movable abutmentcontrolling a return passage from said chamber to said reservoir andmovable through a range of positions corresponding to variations in thepressure of liquid in said chamber, and means responsive to hydraulicpressure created upon sudden movement of said abutment from one positionto another for actuating said brake release means.

8. A brake controlling equipment for governing operation of the brakesfor a vehicle wheel, comprising brake release means operable to effectquick release of the brakes, a casing structure having a liquid supplyreservoir and a pressure chamber, pump means mounted in said casingstructure and operative by saidwheel to supply liquid from saidreservoir to said chamber according to the rotative speed of the wheel,a spring, a movable abutment biased by said spring toward a normalposition and movable therefrom by the pressure of liquid supplied tosaid chamber for varying the flow area of a return passage leadingtherefrom to said reservoir, a piston secured to said movable abutmentand movable thereby through a bore formed within said casing structure,said piston having a restricted port providing communication from saidbore to said chamber, and. means responsive to the force of said springtransmitted by means of liquid in said bore for causing operation ofsaid brake release means.

9. Deceleration control apparatus for governing the operation of. thebrakes for a vehicle wheel, comprising electroresponsive brake releasemeans operable to effect release of the brakes, switch means operativeto close a circuit for energizing said electroresponsive means, a casingstructure having a liquid supply reservoir and a pressure chamber,pumping means mounted in said casing structure and operative by saidvehicle wheel to supply liquid from said reservoir to said chamberaccording to the rotative speed of the wheel, a movable abutment biasedtoward a normal position and movable therefrom under the pressure ofliquid in said chamber for varying the flow area of a return passageleading from said chamber to said reservoir, a piston mounted in a borein said casing structure and operative upon movement of said movableabutment from its normal position to effect flow of liquid from saidchamber to said bore by way of a restricted port, and means responsiveto a force transmitted through the medium of liquid in said bore, due tosudden movement of said movable abutment and piston toward the normalposition, for actuating said switch means.

BURTON S. AIKMAN.

